Raw soybean oil and other raw vegetable oils are refined to remove mucilage, whereby phosphatides such as lecithin and other accompanying hydrophilic components are removed. That process may be called "wet refining to remove mucilage" if it is carried out by extraction with water. In that treatment, a part of the phosphatides is left in the oil; that part is described by the generic term "non-hydratable phosphatides" (NHP). In the production of edible oils, it is essential to remove the NHP content. It is generally believed that the phosphorus content should not exceed 5 parts per million (ppm). (See Hermann Pardun, Die Pflanzenlecithine, Verlag fur chemische Industrie H. Ziolkowsky KG, Augsburg, 1988, pages 181-194).
NHP are formed by the action of enzymes inherent in the plants. In the "Alcon process", enzymes are inactivated by a treatment of soybean flakes with steam to inhibit the formation of NHP and the phosphatide content can be almost entirely removed when the raw oil is wet refined to remove mucilage.
A substantial part of the NHP can be extracted from oil which has been refined to remove mucilage by using aqueous solutions of surfactants (tensides), but, as a rule, a content below 30 ppm cannot not reached. Treatment with acids or alkalies is more successful, but requires many operational steps.